nasmlib/mmap.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 1996-2017 The NASM Authors - All Rights Reserved
   4  *   See the file AUTHORS included with the NASM distribution for
   5  *   the specific copyright holders.
   6  *
   7  *   Redistribution and use in source and binary forms, with or without
   8  *   modification, are permitted provided that the following
   9  *   conditions are met:
  10  *
  11  *   * Redistributions of source code must retain the above copyright
  12  *     notice, this list of conditions and the following disclaimer.
  13  *   * Redistributions in binary form must reproduce the above
  14  *     copyright notice, this list of conditions and the following
  15  *     disclaimer in the documentation and/or other materials provided
  16  *     with the distribution.
  17  *
  18  *     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  19  *     CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  20  *     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  21  *     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  22  *     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  23  *     CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  *     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  25  *     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  26  *     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  *     HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  28  *     CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  29  *     OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
  30  *     EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  31  *
  32  * ----------------------------------------------------------------------- */
  33
  34 #include "file.h"
  35
  36 /* ----------------------------------------------------------------------- *
  37  *   Unix-style memory mapping, using mmap().
  38  * ----------------------------------------------------------------------- */
  39 #if defined(HAVE_FILENO) && defined(HAVE_MMAP)
  40
  41 /*
  42  * System page size
  43  */
  44
  45 /* File scope since not all compilers like static data in inline functions */
  46 static size_t nasm_pagemask;
  47
  48 static size_t get_pagemask(void)
  49 {
  50     size_t ps = 0;
  51
  52 # if defined(HAVE_SYSCONF) && defined(_SC_PAGESIZE)
  53     ps = sysconf(_SC_PAGESIZE);
  54 # elif defined(HAVE_GETPAGESIZE)
  55     ps = getpagesize();
  56 # elif defined(PAGE_SIZE)
  57     ps = PAGE_SIZE;
  58 # endif
  59
  60     nasm_pagemask = ps = is_power2(ps) ? (ps - 1) : 0;
  61     return ps;
  62 }
  63
  64 static inline size_t pagemask(void)
  65 {
  66     size_t pm = nasm_pagemask;
  67
  68     if (unlikely(!pm))
  69         return get_pagemask();
  70
  71     return pm;
  72 }
  73
  74 /*
  75  * Try to map an input file into memory
  76  */
  77 const void *nasm_map_file(FILE *fp, off_t start, off_t len)
  78 {
  79     const char *p;
  80     off_t  astart;              /* Aligned start */
  81     size_t salign;              /* Amount of start adjustment */
  82     size_t alen;                /* Aligned length */
  83     const size_t page_mask = pagemask();
  84
  85     if (unlikely(!page_mask))
  86         return NULL;            /* Page size undefined? */
  87
  88     if (unlikely(!len))
  89         return NULL;            /* Mapping nothing... */
  90
  91     if (unlikely(len != (off_t)(size_t)len))
  92         return NULL;            /* Address space insufficient */
  93
  94     astart = start & ~(off_t)page_mask;
  95     salign = start - astart;
  96     alen = (len + salign + page_mask) & ~page_mask;
  97
  98     p = mmap(NULL, alen, PROT_READ, MAP_SHARED, fileno(fp), astart);
  99     return unlikely(p == MAP_FAILED) ? NULL : p + salign;
 100 }
 101
 102 /*
 103  * Unmap an input file
 104  */
 105 void nasm_unmap_file(const void *p, size_t len)
 106 {
 107     const size_t page_mask = pagemask();
 108     uintptr_t astart;
 109     size_t salign;
 110     size_t alen;
 111
 112     if (unlikely(!page_mask))
 113         return;
 114
 115     astart = (uintptr_t)p & ~(uintptr_t)page_mask;
 116     salign = (uintptr_t)p - astart;
 117     alen = (len + salign + page_mask) & ~page_mask;
 118
 119     munmap((void *)astart, alen);
 120 }
 121
 122 /* ----------------------------------------------------------------------- *
 123  *   No memory map support at all
 124  *   XXX: Add a section with Windows support
 125  * ----------------------------------------------------------------------- */
 126 #else
 127
 128 const void *nasm_map_file(FILE *fp, off_t start, off_t len)
 129 {
 130     (void)fp; (void)start; (void)len;
 131     return NULL;
 132 }
 133
 134 void nasm_unmap_file(const void *p, size_t len)
 135 {
 136     (void)p; (void)len;
 137 }
 138
 139 #endif